Parking brake for an electric vehicle with multi-speed gearbox

ABSTRACT

A commercial vehicle with at least one driven axle, at least one service brake, at least one propulsion engine, and wheels characterized in that the parking brake function of the vehicle is solved by a bistable locking means acting on both wheels. At least one multi-speed gearbox is provided to concurrently activate a first gear stage and a second gear stage having different ratios.

BACKGROUND

Commercial vehicles may utilize a braking system where friction isapplied to prevent one or more vehicle wheels from rotating. In someembodiments, the braking system may be implemented using a combinationcylinder that includes both service brake and parking brake portions.The parking brake function may be realized using a spring brake placedaxially behind the service brake portion in the combination cylinderhousing, which may result in a relatively large assembly.

BRIEF SUMMARY

According to an embodiment of the disclosed subject matter, a vehicledrivetrain may be provided for achieving a bistable locking parkingbrake function. The vehicle drivetrain may include a first multi-speedgearbox having a plurality of driving stages and at least one actuatorto activate a first driving stage of the plurality of driving stages. Afirst actuator of the at least one actuator may activate the firstdriving stage concurrently with a second driving stage. The vehicledrivetrain may further include a second actuator of the at least oneactuator may active the second driving stage concurrently with the firstdriving stage activated by the first actuator. The vehicle drivetrainmay further include a second multi-speed gearbox. The second multi-speedgearbox may include a plurality of driving stages and a third and fourthactuator to concurrently activate a first driving stage and a seconddriving stage of the plurality of driving stages. The vehicle drivetrainmay further include an output shaft lock to mechanically couple anoutput of the first multi-speed gearbox with an output of the secondmulti-speed gearbox while the first driving stage and the second drivingstage are concurrently activated. The activated second driving stage maybe of the plurality of driving stages of the first multi-speed gearboxor of the plurality of driving stages of the second multi-speed gearbox.The vehicle drivetrain may further include an input shaft lock, whenactivated, to mechanically couple an input of the first multi-speedgearbox with an input of the second multi-speed gearbox. The vehicledrivetrain may further include an output shaft lock, when activated, tomechanically couple an output of the first multi-speed gearbox with anoutput of the second multi-speed gearbox. The first and second drivingstages may have different ratios. The vehicle drivetrain may furtherinclude an auxiliary device to manually deactivate the first drivingstage or the second driving stage, thereby releasing the parking brakefunction. The vehicle drivetrain may further include a first clutch ofthe first multi-speed gearbox to engage the first driving stage via thefirst actuator. The vehicle drivetrain may further include a secondclutch of the first multi-speed gearbox to engage the second drivingstage via a second actuator. The vehicle drivetrain may further includean elastic coupling mechanically linked to the second clutch. Theelastic coupling may permit rotation of an input of the firstmulti-speed gearbox to align the first clutch with the first drivingstage while the second clutch is engaged with the second driving stage.

A commercial vehicle may include at least one driven axle, at least oneservice brake, at least one propulsion engine and wheels characterizedin that the parking brake function of the vehicle may be solved by abistable locking means acting on both wheels. The commercial vehicle mayfurther include a first multi-speed gearbox having a first gear stageactivated by a first actuator and coupled to a first wheel of thewheels. The commercial vehicle may further include a second multi-speedgearbox having a second gear stage activated by a second actuator andcoupled to a second wheel of the wheels. The parking brake function maybe achieved by concurrently activating the first gear stage and thesecond gear stage. The commercial vehicle may further include an outputshaft lock, when activated, to couple the first wheel of the pair ofwheels to the second wheel of the pair of wheels. The commercial vehiclemay further include an input shaft lock, when activated, to couple aninput of the first multi-speed gearbox with an input of the secondmulti-speed gearbox. The first gear stage may be characterized by afirst ratio that differs from a second ratio of the second gear stage.The commercial vehicle may further include an elastic coupler and asliding clutch including a toothed selector ring coupled to the elasticcoupler that allows for limited rotational movement of the toothedselector ring about a sliding axis of the sliding clutch. The slidingclutch may be actuated by the second actuator. The commercial vehiclemay further include a multi-speed gearbox having a plurality of gearstages, an actuator, and a sliding clutch, when actuated by theactuator, to engage a first gear stage and a second gear stageconcurrently. The first gear stage or second gear stage may includeconjugated teeth. The teeth of the toothed selector ring are shaped toallow meshing with the conjugated teeth when in a tooth-to-toothposition. The commercial vehicle may further include an outer planetarygear disposed in an outer wheel rim of each wheel of the wheels of thedriven axle. The ratio between a final stage shaft of a differentialdriving the pair of wheels and the driven wheel may be larger than one.The commercial vehicle may further include a hand control unit toactivate the bistable locking means when the commercial vehicle is at astandstill. The commercial vehicle may further include an electronicbrake control unit. The hand control unit may be configured to send abrake request via an electronic signal to a brake control unit toactivate the bistable locking means. The commercial vehicle may furtherinclude a redundant foot brake module for redundant braking and abooster. The hand control unit may be configured to send a brake requestto the booster via an electronic signal to activate the redundant footbrake module when the electronic brake control unit fails to execute thebrake request.

Additional features, advantages, and embodiments of the disclosedsubject matter may be set forth or apparent from consideration of thefollowing detailed description, drawings, and claims. Moreover, it is tobe understood that both the foregoing summary and the following detaileddescription are illustrative and are intended to provide furtherexplanation without limiting the scope of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosed subject matter, are incorporated in andconstitute a part of this specification. The drawings also illustrateembodiments of the disclosed subject matter and together with thedetailed description serve to explain the principles of embodiments ofthe disclosed subject matter. Features from the illustrated embodimentsmay be combined together, appended, removed, and/or otherwise modifiedas desired without departing from the scope of the disclosed subjectmatter. No attempt is made to show structural details in more detailthan may be necessary for a fundamental understanding of the disclosedsubject matter and various ways in which it may be practiced.

FIG. 1 illustrates an example drivetrain 100 in accordance with anembodiment of the disclosed subject matter.

FIG. 2A illustrates an example drivetrain 200 in accordance with anembodiment of the disclosed subject matter.

FIG. 2B illustrates an example drivetrain 275 in accordance with anembodiment of the disclosed subject matter.

FIG. 3 illustrates an example drivetrain 300 in accordance with anembodiment of the disclosed subject matter.

FIG. 4 illustrates an example drivetrain 400 in accordance with anembodiment of the disclosed subject matter.

FIG. 5 illustrates an example drivetrain 500 in accordance with anembodiment of the disclosed subject matter.

FIG. 6 illustrates an example drivetrain 600 in accordance with anembodiment of the disclosed subject matter.

FIG. 7 illustrates an example drivetrain 700 in accordance with anembodiment of the disclosed subject matter.

FIGS. 8A and 8B illustrate example drivetrains 800 and 825 in accordancewith embodiments of the disclosed subject matter.

FIG. 9 illustrates an example flow 900 for activating a parking brakefunction in accordance with an embodiment of the disclosed subjectmatter.

FIG. 10 illustrates an example flow 1000 for activating a parking brakefunction in accordance with an embodiment of the disclosed subjectmatter.

FIG. 11 shows a computing device 20 according to an embodiment of thedisclosed subject matter.

FIG. 12 shows a network configuration according to an embodiment of thedisclosed subject matter.

FIG. 13 illustrates an example partial system configuration for enablingthe secondary brake functionality in accordance with an embodiment ofthe disclosed subject matter.

FIG. 14 illustrates an example partial system configuration for enablingthe secondary brake functionality in accordance with an embodiment ofthe disclosed subject matter.

DETAILED DESCRIPTION

The present subject matter discloses a parking brake function that maybe realized using one or more multi-speed gearboxes. The present subjectmay be especially advantageous in commercial trucks having electric orhybrid drivetrains, though it may be applicable to any vehicle havingany type of drivetrain employing one or more multi-speed gearboxes. Insome embodiments, the present subject matter may allow for the size andcomplexity of the vehicle braking system to be reduced particularly inproximity to the wheels and/or axles. This may reduce the overallvehicle weight and/or allow additional and/or alternate vehiclecomponents, such as batteries, electric motors, and the like, to beinstalled in the vehicle.

FIG. 1 is a schematic of a drivetrain 100 according to an embodiment ofthe disclosed subject matter having an example differential 5. Thedrivetrain 100/150 may include a shift-able, multi-speed gearbox 8having at least a first driving stage i(1) and a second driving stagei(2). The driving stages i(1)/i(2) may utilize different ratios foroperating an electric motor 1 in the optimal performance range duringvarious driving situations. Rotation from the electric motor 1 or otherpropulsion source may be input to the multi-speed gearbox 8 via an inputshaft, chain, belt, gear, or the like, of the multi-speed gearbox 8. Theratios may be selected, for example, to fulfill a vehicle gradeabilityrequirement from rest, such that the vehicle may be capable of startingon a specified grade and capable of maintaining forward motion on thesame grade. While referred to as “gearbox,” the driving stages i(1)/i(2)disposed within multi-speed gearbox 8 may be realized by gears, pulleysor sprockets, which are connected by belts and/or chains, or the like. Adifferential 5 may distribute the torque generated by the electric motor1 to a wheel pair 7. Each wheel of wheel pair 7 may include an outerplanetary gear disposed on the outer rim of each wheel, where a ratiobetween a final stage shaft of the differential 5 driving the wheel pair7 and the driven wheels is larger than one. While an electric motor 1 isillustrated in FIG. 1 for the purpose of discussion, any type of engine,motor, or other source of propulsion may be used without departing fromthe scope of the disclosed subject matter. Where one or more electricmotors may be utilized, the vehicle may include an appropriate chargestorage device, such as a battery pack, capacitor, or the like, fromwhich current may be principally drawn to deliver power. A gear actuator3, which may be electrically, hydraulically, or pneumatically operated,may select a driving stage i(1)/i(2) of the multi-speed gearbox 8 usinga sliding clutch 4. The gear actuator 3 may also select a neutral mode(N) of sliding clutch 4, which may render the output shaft of theelectric motor 1 disconnected from the differential 5 and wheels 7. Asused herein, the output shaft of the electric motor 1 may bemechanically coupled to the input of the multi-speed gearbox 8, and theconventions may be used interchangeably. For example, sliding clutch 4may be said to couple the output of electric motor 1, or equivalentlythe input of the multi-speed gearbox 8, to the driving stages i(1)/i(2),differential 5, and wheels 7. As shown, when gear actuator 3 is moved toa first mode (1), the sliding clutch 4 may mechanically link the outputshaft of the electric motor 1 to the differential 5 and wheels 7 via afirst driving stage i(1). When gear actuator 3 is moved to a second mode(2), the sliding clutch 4 may mechanically link the output shaft of theelectric motor 1 to the differential 5 and wheels 7 via a second drivingstage i(2). A fourth locking mode (L) may mechanically link the electricmotor 1 to the differential 5 and wheels 7 via both the first i(1) andsecond i(2) driving stages. As previously discussed, the at least firstand second driving stages i(1)/i(2) may utilize differing ratios thatcannot operate simultaneously without allowing at least one drivingstage i(1)/i(2) to slip. Accordingly, the fourth locking mode (L) maylock the multi-speed gearbox 8 such that it prevents rotation both ofits output shaft and the mechanically-coupled output shaft of theelectric motor 1.

With the locking mode (L) engaged, the input gear-wheel of thedifferential, also known as the pinion gear, may be locked as well asthe ring gear. Each wheel of wheel pair 7 may be able to independentlyrotate freely in opposite directions, while each wheel may be prohibitedfrom simultaneously rotating in the same direction. To ensure thevehicle is prevented from rolling, a differential lock 6 may beutilized. A differential lock 6 may be activated to mechanically linkthe first wheel with the second wheel, thereby preventing theindependent rotation in opposite directions. The differential lock 6 maybe realized by coupling each output shaft of the differential 5. Withthe wheel pair 7 locked, a parking brake mode may be achieved that mayprevent the vehicle from rolling forward and/or backward. Differentiallock 6 may be activated to mechanically link the wheels 7 subsequentlyin response to or simultaneously with the selection of the fourthlocking mode (L) via gear actuator 3. Alternatively or in addition, thedifferential lock 6 may be activated independently of whether the fourthlocking mode (L) is activated for the purpose of improving wheeltraction, for example. Activation of the fourth locking mode (L) by gearactuator 3 shall be prohibited while the vehicle is moving, viamechanical and/or electrical techniques, to avoid causing damage to thefirst and second driving stages i(1)/i(2).

The multi-speed gearbox 8 may be unsynchronized. In order to transitionbetween the driving stages i(1)/i(2), a variety of techniques may beemployed. For example, while the vehicle is moving, a transition from afirst driving stage i(1) to i(2) may occur by disengaging the firstdriving stage i(1) such that electric motor 1 is in a neutral mode.Subsequently, the speed of the output shaft of the electric motor 1 andthe coupled input of the multi-speed gearbox 8 may be adjusted so thatthe sliding clutch 4 can engage with the driving stage i(2) smoothly andwithout causing excessive wear or damage. In contrast, when the vehicleis at a standstill, the electric motor 1 may rotate the input of themulti-speed gearbox 8 to a position where the sliding clutch 4 mayengage with the second driving stage i(2). If the input of themulti-speed gearbox 8 is not aligned such that the sliding clutch 4 canengage with the second driving stage i(2), the input of the multi-speedgearbox 8 may be additionally rotated via the electric motor 1, whichmay correspondingly rotate the vehicle wheels 7, until the correctengagement position for the second driving stage i(2) is reached.Rotating the wheels 7 may displace the vehicle by a short distance, suchas between 5 and 25 mm; preferably, 14 mm or less. A gear actuator 3,which may also be used to activate clutch 4 to engage the first orsecond driving stage i(1)/i(2), may also be used to disengage the clutch4 from the first driving stage i(1)/i(2).

The multi-speed gearbox 8 may be unsynchronized such that a connectedelectric motor may adjust its speed appropriately to allow for a smoothtransition of the sliding clutch 4 based on the selected driving stagei(1)/i(2) and current vehicle speed. A smooth transition from onedriving stage to another may be one that is designed to minimize wear onthe internal multi-speed gearbox 8 components while also providing acomfortable experience for passengers of the vehicle that is relativelyfree of rapid accelerations and decelerations.

FIG. 2A is a schematic of a drivetrain 200 according to an embodiment ofthe disclosed subject matter having an example differential 5.Drivetrain 200/250 may be similar to drivetrain 100/150 but may includetwo gear actuators 3A/3B that are individually operable via a respectivesliding clutch 4A/4B. As shown in FIG. 2, a neutral mode (N) may beselected where neither gear actuator 3A nor 3B is activated to engageits respective sliding clutch 4A/4B. When gear actuator 3A is activatedin a first mode (1), the corresponding sliding clutch 4A may link theoutput shaft of electric motor 1 to the differential 5 and wheels 7 viaa first driving stage i(1). When gear actuator 3B is activated and gearactuator 3A is not activated in a second mode (2), the correspondingsliding clutch 4B may be engaged to link the output shaft of electricmotor 1 to the differential 5 and wheels 7 via a second driving stagei(2). A fourth locking mode (L) may occur where both gear actuator 3Aand gear actuator 3B are activated to engage sliding clutches 4A and 4Bto mechanically link the output shaft of the electric motor 1 with bothdriving stages i(1)/i(2). Because the first and second driving stagesmay utilize differing ratios that cannot operate concurrently, thefourth locking mode (L) may lock the drivetrain 200/250 to prevent thevehicle wheels 7 from rolling, thereby achieving a parking brakefunction when the differential lock is activated.

As previously discussed with respect to FIG. 1, with the locking mode(L) engaged, the input gear-wheel of the differential may be locked.Each wheel of wheel pair 7 may be able to independently rotate freely inopposite directions, while each wheel may be prohibited fromsimultaneously rotating in the same direction. To ensure the vehicle isprevented from rolling, a differential lock 6 may be utilized. Adifferential lock 6 may be activated to mechanically link the firstwheel with the second wheel, thereby preventing the independent rotationin opposite directions. The differential lock 6 may be realized bycoupling each output shaft of the differential 5. With the wheel pair 7now locked, parking brake function may be achieved. Differential lock 6may be activated to mechanically link the wheels 7 subsequently inresponse to, or simultaneously with the selection of the fourth lockingmode (L) via gear actuator 3. Alternatively or in addition, thedifferential lock 6 may be activated independently of whether the fourthlocking mode (L) is activated. This may be performed for the purpose ofimproving wheel traction, for example. Activation of the fourth lockingmode (L) by gear actuator 3 may be prohibited while the vehicle is inmotion via mechanical and/or electrical techniques to avoid causingdamage to the first and second driving stages i(1)/i(2).

FIG. 2B is a schematic of a drivetrain 275 according to an embodiment ofthe disclosed subject matter that is similar to drivetrain 200 asdepicted in FIG. 2A. In drivetrain 275, sliding clutch 4B may bemechanically linked to an elastic coupling and may be only activated viagear actuator 3B during a parking brake mode (L). As in drivetrain 200,gear actuators 3A/3B may be individually operable via the respectivesliding clutches 4A/4B. In contrast to drivetrain 200, sliding clutch 4Amay be used during driving modes to engage both the first driving stagei(1) and the second driving stage i(2); i.e., the first (1) and second(2) modes. Sliding clutch 4B may only be used during the parking brakemode (L) and may remain in a neutral mode (N) at all other times.Therefore, the elastic coupling of sliding clutch 4B may not be usedwhile the vehicle is moving. As in drivetrain 200, the first i(1) andsecond i(2) driving stages may utilize differing ratios that cannotoperate concurrently. Thus, the fourth locking mode (L) may lock thedrivetrain 275 to prevent the vehicle wheels 7 from rolling, therebyachieving a parking brake function.

As previously discussed with respect to FIG. 1, with the locking mode(L) engaged, the input gear-wheel of the differential may be locked.Each wheel of wheel pair 7 may be able to independently rotate freely inopposite directions, while each wheel may be prohibited fromsimultaneously rotating in the same direction. To ensure the vehicle isprevented from rolling, a differential lock 6 may be utilized. Adifferential lock 6 may be activated to mechanically link the firstwheel with the second wheel, thereby preventing the independent rotationin opposite directions. The differential lock 6 may be realized bycoupling each output shaft of the differential 5. Differential lock 6may be activated to mechanically link the wheels 7 subsequently inresponse to, or simultaneously with the selection of the fourth lockingmode (L) via gear actuator 3. Alternatively or in addition, thedifferential lock 6 may be activated independently of whether the fourthlocking mode (L) is activated. This may be performed for the purpose ofimproving wheel traction, for example. Activation of the fourth lockingmode (L) by gear actuator 3 may be prohibited while the vehicle is inmotion via mechanical and/or electrical techniques to avoid causingdamage to the first and second driving stages i(1)/i(2).

The elastic coupling, which is mechanically linked with sliding clutch4B, may improve the parking process and facilitate engagement of theparking brake function. When attempting to park the vehicle, the vehiclemay then be maneuvered into the desired parking location. At this point,the driver may wish to activate the parking brake function. Formaneuvering, stage i(1) is activated and stays activated. Parking modeis initiated by activating stage i(2) with sliding clutch 4B. To avoiddriving the electric motor in case of an unaligned clutch 4B and gearwheel of stage i(2), the elastic coupling of the clutch and the chamferor tooth-on-tooth engagement of the second driving stage i(2) is used.The elastic coupler will rotate under the same force as the actuatorforce when the clutch 4B is engaged.

In another example, sliding clutch 4B may be engaged via gear actuator3B to activate the second driving stage i(2). When stopped, theengagement of sliding clutch 4B with the second driving stage i(2) mayoccur only when the hub of the second driving stage i(2) is correctlyaligned with sliding clutch 4B. For example, sliding clutch 4B mayinclude dog teeth, a toothed selector ring, or the like, that may bealigned with a corresponding toothed portion of the driving stage i(2).The driving stages i(1)/i(2) may include conjugated teeth that areshaped to mesh with the teeth of the toothed selector ring of clutch4A/4B when in a tooth-to-tooth position. Electric motor 1 may rotate theinput of multi-speed gearbox 8 to align the teeth of sliding clutch 4Bwith the second driving stage i(2). To achieve the parking brakefunction, driving stage i(1) may be concurrently engaged via slidingclutch 4A. Sliding clutch 4A may also require alignment with the hub ofdriving stage i(1), which can be accomplished by rotating the input ofmulti-speed gearbox using electric motor 1 as previously described.Normally, rotating the electric motor 1 at this point to align clutch 4Awith driving stage i(1) would displace the vehicle, since driving stagei(2) is already engaged. Because clutch 4B is mechanically linked to theelastic coupling however, limited rotation of the input may be permittedwithout displacing the vehicle. Stated another way, the elastic couplingof sliding clutch 4B allows the input of multi-speed gearbox 8 to twistin-place without translating the twisting to rotation of the wheel pair7 via the second driving stage i(2), as may be the case when an elasticcoupling is not used. In this way, alignment of the first driving stagei(1) hub may be achieved with clutch 4A while the second driving stagei(2) is engaged without displacing the vehicle.

FIG. 3 is a schematic of a drivetrain 300 that may include a pair ofelectric motors 1/2 and corresponding pair of multi-speed gearboxes8A/8B according to an embodiment of the disclosed subject matter. Eachof the first electric motor 1 and the second electric motor 2 mayindividually drive a respective wheel of the wheel pair 7 via arespective first and second multi-speed gearbox 8A/8B. In this way, andas applicable to FIGS. 4-7, the vehicle may realize the associatedimprovements in efficiency, due to no losses through the differential,safety, due to the second motor being available in case of loss of thefirst motor, and dynamics, due to torque vectoring. Additionally, eachwheel of wheel pair 7 may realize individualized braking andindividualized recuperation to recharge an associated charge storagedevice of the vehicle. Rotation from the electric motor 1 or otherpropulsion source may be input to the multi-speed gearboxes 8A/8B via aninput shaft, chain, belt, gear, or the like, of the multi-speed gearbox8A/8B. Each multi-speed gearboxes 8A/8B may have two or more drivingstages i(1)/i(2) that may be individually engaged via a correspondingsliding clutch 4A-4D by activating a corresponding gear actuator 3A-3D.In this way, each multi-speed gearbox 8A/8B may provide at least aneutral, first, and second driving mode as previously discussed. In anembodiment, gear actuators 3A/3C and 3B/3D may be activated anddeactivated in pairs simultaneously, so as to maintain a same drivingstage i(1)/i(2) for each of the wheels 7. For example, the actuation ofthe i(1) driving stage may occur simultaneously for gear actuators 3Aand 3C and sliding clutches 4A and 4C, while actuation of the i(2)driving stage may occur simultaneously for gear actuators 3B and 3D andsliding clutches 4B and 4D. Activating gear actuators 3A-3D together mayeach input of the multi-speed gearboxes 8A/8B corresponding wheels ofthe wheel pair 7. With the wheel pair 7 locked, a parking brake mode maybe achieved. Since each wheel of the wheel pair 7 may be drivenindependently, no differential may be necessary to distribute torque tothe wheels 7. Likewise, and in contrast to the drivetrain layouts 100and 200, no differential lock may be necessary in order to lock thewheels 7 in drivetrain layout 300.

FIG. 4 is a schematic of a drivetrain 400 similar to drivetrain 300 thatmay additionally include shaft lock 12 according to an embodiment of thedisclosed subject matter. Shaft lock 12 may be activated to mechanicallycouple each wheel of the wheel pair 7. Unlike drivetrain 300, if shaftlock 12 is activated, activating either of gear actuators 3A and 3B orgear actuators 3C and 3D may lock both wheels of wheel pair 7. Statedanother way, shaft lock 12 may allow for locking both wheels of thewheel pair 7 by locking only a single multi-speed gearbox of themulti-speed gearboxes 8A/8B. With the wheel pair 7 locked via shaft lock12, the parking brake mode may be achieved. As previously discussed, oneor more multi-speed gearboxes 8A/8B may be locked in a fourth lockingmode (L) where at least two driving stages i(1)/i(2) are engagedconcurrently.

FIG. 5 is a schematic of a drivetrain 500 where common gear actuators 3Aand 3B are shared between the sliding clutches 4A-4D according to anembodiment of the disclosed subject matter. More specifically, gearactuator 3A may be used to engage sliding clutches 4A and 4D that maymechanically link to a first driving stage i(1). Gear actuator 3B may becorrespondingly used to engage sliding clutches 4B and 4C, which maymechanically link to a second driving stage i(2). With both gearactuators 3A and 3B activated to engage all four clutches 4A-4D, thewheel pair 7 may be locked, thereby achieving the parking brake mode. Byreducing the number of gear actuators 3 used to implement the drivetrain500 when compared to drivetrain 400, a cost savings may be realized.Additionally, because drivetrain 500 may operate the sliding clutches4A/4D and 4B/4C in unison, a differential lock 6 may be unnecessary inorder to lock both wheels of wheel pair 7 since both the firstmulti-speed gearbox 8A may be locked concurrently with the secondmulti-speed gearbox 8B.

FIG. 6 is a schematic of a drivetrain 600 according to an embodiment ofthe disclosed subject matter. As shown in FIG. 6, gear actuators 3A and3B may be provided for mechanically linking the output shaft of electricmotor 1 with multi-speed gearbox 8A via first and second slidingclutches 4A and 4B. Gear actuator 3A may be deactivated in a neutralmode or activated to engage sliding clutch 4A with at least a firstdriving stage i(1), while gear actuator 3B may be deactivated in aneutral mode or activated to engage sliding clutch 4B with a seconddriving stage i(2). Using gear actuator 3A to engage clutch 4A in thefirst driving stage i(1) while simultaneously using gear actuator 3B toengage clutch 4B in the second driving stage i(2) may achieve theparking brake mode for a first wheel of the wheel pair 7. Gear actuator3C, on the other hand, may be deactivated in a neutral mode or activatedto engage either at least a first driving stage i(1) or a second drivingstage i(2) of multi-speed gearbox 8B via sliding clutch 4C. Becausesliding clutch 4C may be incapable of engaging both driving stagesi(1)/i(2) simultaneously to establish a fourth locking mode, shaft lock12 may be utilized to lock the second wheel when the first wheel islocked via the engagement of sliding clutches 4A and 4B. Stated anotherway, the shaft lock 12, when activated, may lock the second wheel(corresponding to electric motor 2) to the locked first wheel(corresponding to electric motor 1).

In the event of a failure of one of the electric motors 1/2 orassociated electronics, such as an inverter, power supply line, or thelike, the remaining electric motor 1/2 and corresponding multi-speedgearbox 8A/8B may be utilized to transfer power to both wheels of wheelpair 7 by activating shaft lock 12. For example, if electric motor 1fails, electric motor 2 may provide power to both wheels of wheel pair 7by engaging shaft lock 12. Following the same example, even whereelectric motor 1 fails, the vehicle may still achieve a parking brakemode by activating shaft lock 12 in conjunction with engaging bothclutches 4A and 4B or, by engaging clutch 4C with a first driving stagei(1)/i(2) while concurrently engaging either clutch 4A or 4Bcorresponding to the second, different driving stage i(1)/i(2).

FIG. 7 is a schematic of a drivetrain 700 having a first and secondshaft lock 12A/12B according to an embodiment of the disclosed subjectmatter. The shaft locks 12A/12B may each be operated by one or more gearactuators or by the same gear actuator. Drivetrain 700 includes a firstgear actuator 3A and a second gear actuator 3B that may functionsimilarly to gear actuator 3C of drivetrain 600 having at least threedriving modes. Specifically, each of gear actuators 3A and 3B may bedeactivated in a neutral mode or activated to engage a respectivesliding clutch 4A/4B with either a first driving stage i(1) or a seconddriving stage i(2) of a respective multi-speed gearbox 8A/8B. Ingeneral, gear actuators 3A and 3B may be synchronized to engage thefirst driving stage i(1) or the second driving stage i(2) simultaneouslyor otherwise during the same time period, as previously discussed withreference to drivetrain 400. Where driving conditions differ for eachwheel of the wheel pair 7, for example, such as in ice or snow, or whiletraveling off-road, it may be possible to drive the first wheel usingelectric motor 1 at a first speed using the first driving stage i(1) andto simultaneously drive the second wheel using electric motor 2 at asecond speed using the second driving stage i(2). Like gear actuator 3Cof drivetrain 600, neither of the gear actuators 3A/3B may individuallyengage both the first and second driving modes i(1)/i(2) simultaneously,which may prevent either gear actuator 3A/3B from individuallyestablishing a fourth locking mode. To achieve the parking brake mode indrivetrain 700 then, gear actuators 3A and 3B may each select differentdriving stages i(1)/i(2) via sliding clutches 4A and 4B. For example,gear actuator 3A may select driving stage i(2) while gear actuator 3Bmay select driving stage i(1). A shaft lock 12B may be disposed therebetween to mechanically couple the first and second wheels of wheel pair7. Shaft lock 12B alone may be insufficient to realize the parkingbrake, however, since for example, the vehicle wheels 7 may still becapable of rolling, though the corresponding electric motors mayindependently rotate at differing speeds as a result of the disparatedriving stages engaged. Accordingly, a shaft lock 12A may be provided tocouple the output shafts of the electric motors, or equivalently theinputs of multi-speed gearboxes 8A/8B, thereby inhibiting theindependent rotation. When activated during the same time, shaft locks12A and 12B may achieve the parking brake function that locks drivetrain700.

In the event of a failure of one of the electric motors 1/2 or one ofthe multi-speed gearboxes 8A/8B, the remaining electric motor 1/2 andcorresponding multi-speed gearbox 8A/8B may be utilized to transferpower to both wheels of wheel pair 7 by activating shaft lock 12B. Forexample, if electric motor 1 fails, electric motor 2 may provide powerto both wheels of wheel pair 7 via engagement of shaft lock 12B whileshaft lock 12A and clutch 4A remain disengaged to eliminate and/orreduce any possible drag from the failed electric motor 1.Alternatively, or in addition, should a problem arise within multi-speedgearbox 8A, for example, shaft lock 12B may be utilized in combinationwith shaft lock 12A to transfer the cumulative power from both electricmotors 1/2 via sliding clutch 4B and multi-speed gearbox 8B to the wheelpair 7. In this case, sliding clutch 4A may remain disengaged in theneutral mode so as to isolate the failed multi-speed gearbox 8A from theremainder of the drivetrain.

For each of the drivetrains shown in FIGS. 1-8, engagement of the atleast two driving stages i(1)/i(2) to achieve the parking brake mode maybe designed such that the parking brake functionality remains even whenpower is removed from the vehicle. This may be implemented usingself-locking or otherwise latching actuators 3, a spring within the gearactuator 3 or sliding clutch 4, or the like. Because the gearactuator(s) 3 may be activated and deactivated via electrical orelectronic techniques, an unlocking mechanism may be provided formanually disengaging the parking brake mode when vehicle power isunavailable and/or available. The unlocking mechanism may be anauxiliary device 9 implemented in the form of a spindle, thread-typedevice, and may be electrical or electronic in-part for use when vehiclepower is available. Alternatively, or in addition, auxiliary device 9may be an electrical or electronic release device that operates viaexternally-provided power that does not originate from the vehicle, suchas from a battery of the auxiliary device 9, household mains electricpower, another vehicle, or other power source. Alternatively, or inaddition, the auxiliary device 9 may be fitted within the passengercompartment of the vehicle and may be electrically coupled with themulti-speed gearbox 8.

FIG. 8A is a schematic of a drivetrain 800 employing a first embodimentof an auxiliary device 9 and having an example differential 5. Theauxiliary device 9 may employ an unlocking mechanism that enables manualrelease of the parking brake. The unlocking mechanism may be implementedusing a spindle, thread-type device, electrical device, or the like, forexample, to enable release of the parking brake mode. As shown in FIG.8A, the auxiliary device 9 may be implemented by allowing for for manualdisengagement of sliding clutches 4A and 4B.

FIG. 8B is a schematic of a drivetrain 825 employing a second embodimentof an auxiliary device 9 and having an example differential 5. Theembodiment shown in FIG. 8B may be integrated with or otherwise combinedwith the embodiment shown in FIG. 8A, although for purposes ofsimplifying the discussion and the illustrations, the embodiments areshown separately. As shown in FIG. 8B, the auxiliary device 9 may employa manual unlocking mechanism to enable release of the parking brake bydisengaging sliding clutches 4A and 4B. Additionally, where gearactuator 3 also activates and deactivates differential lock 6 of thedifferential 5, auxiliary device 9 may also manually unlock thedifferential lock 6.

FIG. 9 shows an example flow 900 for parking a vehicle according to anembodiment of the disclosed subject matter. A request may be received inS901 from a user to park a vehicle having at least one multi-speedgearbox. The parking request may be received via an input disposedwithin the vehicle itself or may be received remotely via an electronicdevice, such as a key fob or cellular phone, and may be received via theInternet, WiFi, Bluetooth, RFID, or other transmission medium. Thevehicle may employ any of the example drivetrain layouts shown in FIGS.1-8 or may employ an alternative drivetrain layout. In S902, it may bedetermined whether the vehicle is currently in motion. If the vehicle isin motion, the service brake may be applied to bring the vehicle torest. The force with which the service brake is applied may beconfigurable and/or may vary based on the vehicle's current speed. Theservice brake may be applied by a processor of the vehicle, by the user,or both. Once the vehicle is at rest, the service brake may be held inS904, either by a processor of the vehicle itself, by the user, or both.At least two driving stages may be concurrently engaged in S905 toachieve the parking brake function. The driving stages may be, forexample, a first driving stage and second driving stage implementedusing gears or the like, as previously discussed. The first and seconddriving stages may be engaged within a single or multiple multi-speedgearbox(es). For example, the first driving stage may be engaged withina first multi-speed gearbox while the second driving stage may beengaged within the second multi-speed gearbox. The engagement of thefirst and second driving stages in S905 may or may not occursimultaneously. For example, the second driving stage may be engagedfirst, followed by the engagement of the first driving stage such thatthe first and second driving stages are concurrently engaged.

The engagement of the first and/or second driving stages may occur afterrotation of the input shaft of the first and/or second multi-speedgearbox in order to correctly align the hub of the driving stage (e.g.,i(1)/i(2)) with the sliding clutch 4. Rotation of the input shaft of themulti-speed gearbox(es) may involve displacing the vehicle forwardand/or reverse by a relatively small distance, such as between 5 and 25mm; preferably, 14 mm or less.

Other drivetrain variants include a single speed gearbox placed betweenone or more electric motors 1/2 and the multi-speed gearbox 8.

FIG. 10 shows an example flow 1000 for releasing a parking brakefunction. In S1001, a request to un-park a vehicle having a multi-speedgearbox 8 may be received from a user. The request may be received viaan input disposed within the vehicle itself or may be received remotelyvia a secure electronic device, such as a key fob or cellular phone, andmay be received via the Internet, WiFi, Bluetooth, RFID, or othertransmission medium. The vehicle may employ any of the exampledrivetrain layouts shown in FIGS. 1-8 or may employ yet an alternativedrivetrain layout. In S1002, the service brake may be applied by aprocessor of the vehicle, by the user, or both. Alternatively, or inaddition, a hill start assist may be activated. A hill start assist mayapply the service brake automatically to prevent the vehicle fromrolling when starting from rest on an incline. In S1003, the vehicle maywait for the selection of a driving gear. The selected gear may be, forexample, a “Drive” gear and may be selected by the user or selectedautomatically by a processor of the vehicle. In response to the gearselection, a processor of the vehicle may cause the disengagement of theat least two concurrent driving stages and to engage a single drivingstage of the multi-speed gearbox 8 in S1004. The disengagement of the atleast two driving stages may occur after rotation of the input shaft ofat least the first and/or second multi-speed gearbox 8 in order tocorrectly align the hub of the driving stage (e.g., i(1)/i(2)) with thesliding clutch 4. Rotation of the input shaft of the multi-speedgearbox(es) 8 may involve displacing the vehicle forward and/or reverseby a relatively small distance, such as between 5 and 25 mm; preferably,14 mm or less. In S1005, the vehicle service brake may be released inresponse to receiving an accelerator request. The accelerator requestmay be transmitted by a processor of the vehicle in response to the userdepressing an accelerator pedal, for example.

Embodiments of the processor-based features of the presently disclosedsubject matter may be implemented in and used with a variety ofcomponent and network architectures. FIG. 11 is an example computingdevice 20 suitable for implementing embodiments of the presentlydisclosed subject matter. The device 20 may be, for example, a desktopor laptop computer, gaming console, gaming server, set-top box, or amobile computing device such as a smart phone, tablet, or the like. Thedevice 20 may include a bus 21 which interconnects major components ofthe computing device 20, such as a central processor 24, a memory 27such as Random Access Memory (RAM), Read Only Memory (ROM), flash RAM,or the like, a user display 22 such as a display screen, a user inputinterface 26, which may include one or more controllers and associateduser input devices such as a keyboard, mouse, touch screen, and thelike, a fixed storage 23 such as a hard drive, flash storage, and thelike, a removable media component 25 operative to control and receive anoptical disk, flash drive, and the like, and a network interface 29operable to communicate with one or more remote devices via a suitablenetwork connection.

The bus 21 allows data communication between the central processor 24and one or more memory components, which may include RAM, ROM, and othermemory, as previously noted. Typically, RAM is the main memory intowhich an operating system and application programs are loaded. A ROM orflash memory component can contain, among other code, the BasicInput-Output system (BIOS) which controls basic hardware operation suchas the interaction with peripheral components. Applications residentwith the computer 20 are generally stored on and accessed via a computerreadable medium, such as a hard disk drive (e.g., fixed storage 23), anoptical drive, floppy disk, or other storage medium.

The fixed storage 23 may be integral with the computer 20 or may beseparate and accessed through other interfaces. The network interface 29may provide a direct connection to a remote server via a wired orwireless connection. The network interface 29 may provide suchconnection using any suitable technique and protocol as will be readilyunderstood by one of skill in the art, including digital cellulartelephone, WiFi, Bluetooth®, near-field, and the like. For example, thenetwork interface 29 may allow the computer to communicate with othercomputers via one or more local, wide-area, or other communicationnetworks, as described in further detail below.

Many other devices or components (not shown) may be connected in asimilar manner (e.g., document scanners, digital cameras and so on).Conversely, all of the components shown in FIG. 11 need not be presentto practice the present disclosure. The components can be interconnectedin different ways from that shown. The operation of a computer such asthat shown in FIG. 11 is readily known in the art and is not discussedin detail in this application. Code to implement the present disclosurecan be stored in computer-readable storage media such as one or more ofthe memory 27, fixed storage 23, removable media 25, or on a remotestorage location.

FIG. 12 shows an example network arrangement according to an embodimentof the disclosed subject matter. One or more devices 10, 11, such aslocal computers, smart phones, tablet computing devices, and the likemay connect to other devices via one or more networks 30. Each devicemay be a computing device as previously described. The network may be alocal network, wide-area network, the Internet, or any other suitablecommunication network or networks, and may be implemented on anysuitable platform including wired and/or wireless networks. The devicesmay communicate with one or more remote devices, such as servers 13and/or databases 15. The remote devices may be directly accessible bythe devices 10, 11, or one or more other devices may provideintermediary access such as where a server 13 provides access toresources stored in a database 15. The devices 10, 11 also may accessremote platforms 17 or services provided by remote platforms 17 such ascloud computing arrangements and services. The remote platform 17 mayinclude one or more servers 13 and/or databases 15.

The user interface 13, database 15, and/or processing units 14 may bepart of an integral system or may include multiple computer systemscommunicating via a private network, the Internet, or any other suitablenetwork. One or more processing units 14 may be, for example, part of adistributed system such as a cloud-based computing system, searchengine, content delivery system, or the like, which may also include orcommunicate with a database 15 and/or user interface 13.

FIG. 13 illustrates an example partial system configuration 1300 forenabling the secondary brake functionality in case of a service brakecontrol failure when dynamic parking brake functionality is notavailable. This parking lock does not allow for braking when the vehicleis in motion, unlike present spring brake type parking brakes.Alternatively, secondary braking via hand control unit can be realized.A hand control unit 1310 may be electrically coupled to an electronicbrake modulator 1330 and electronic braking system (EBS) control unit1320. Alternatively, or in addition, the features of the EBS controlunit 1320 may be implemented using other types of computing devicescapable of being configured to apply the vehicle service brake. Forexample, the features of EBS control unit 1320 may be performed by ageneral-purpose processor or controller configured to executeinstructions stored in a computer-readable storage medium to transformthe general-purpose processor into a special-purpose processing device.The EBS control unit 1320 may implemented using, for example, amicroprocessor, microcontroller, field-programmable gate array (FPGA),application-specific integrated circuit (ASIC), and/or a software modulethat executes on a centralized controller that performs other functionsand/or cooperates with other vehicle systems. In case of a foot brakemodule failure, the driver can activate the service brake via the handcontrol unit 1310. The hand control unit 1310 sends the brake request1380 to the EBS control unit 1320 via an electronic signal. In case ofEBS failure, the hand control unit 1310 sends a brake request 1380 tothe EBM 1330. EBM 1330 is the pneumatic backup that supplies EBSone-channel module 1340 and EBS two-channel module 1350 in case of EBSfailure. Foot Brake Module failures can occur, for example, when abottle is under the pedal and the driver cannot execute the brakerequest with his foot. In an embodiment, the electrical coupling may bevia communications paths 1361/1362, such as a Controller Area Network(CAN). Communications path 1361/1362 may be implemented via two separateand individual point-to-point connections as shown in FIG. 13 or via acommon bus configuration comprising path 1361 and path 1362. Theelectronic brake modulator 1330 may be connected with a pneumatic airsupply 1301 and configured to distribute the air supply 1301 to an EBSone-channel module 1350 and EBS two-channel module 1340. Hand controlunit 1310 may transmit a brake request 1380 via communication path 1361to electronic brake modulator 1330 and a brake request 1380 viacommunication path 1362 to EBS control unit 1320. In response toreceiving brake request 1380, electronic brake modulator 1330 maymodulate air pressure to the EBS one-channel module 140 and EBStwo-channel module 1350.

FIG. 14 illustrates an example partial system configuration 1400 forenabling the secondary brake functionality in case of a service brakecontrol failure when dynamic parking brake functionality is notavailable. A hand control unit 1310 may be electrically coupled to abooster 1410 and electronic braking system (EBS) control unit 1320. Inan embodiment, the electrical coupling may be via communications paths1361/1362, such as a Controller Area Network (CAN). Communications path1361/1362 may be implemented via two separate and individualpoint-to-point connections as shown in FIG. 14 or via a common busconfiguration comprising path 1361 and path 1362. The booster 1410 maybe connected with a pneumatic air supply 1301 and configured to modulatethe air supply 1301 to a redundant foot brake module 1420. Hand controlunit 1310 may transmit a brake request 1380 via communication path 1362to EBS control unit 1320. If the brake request 1380 is not executed,then the brake request 1380 is transmitted via communication path 1361to the booster 1410. In response to receiving pressure request 1380, thebooster 1410 may modulate air pressure to the redundant foot brakemodule 1420. A service brake may be activated by the hand control unit1310 by sending a brake request 1380 to the redundant foot brake module1420 via booster 1410 when the EBS control unit 1320 fails in executingthe brake request 1380.

More generally, various processor-enabled features of the presentlydisclosed subject matter may include or be embodied in the form ofcomputer-implemented processes and apparatuses for practicing thoseprocesses. Embodiments also may be embodied in the form of a computerprogram product having computer program code containing instructionsembodied in non-transitory and/or tangible media, such as floppydiskettes, CD-ROMs, hard drives, USB (universal serial bus) drives, orany other machine readable storage medium, such that when the computerprogram code is loaded into and executed by a computer, the computerbecomes an apparatus for practicing embodiments of the disclosed subjectmatter. Embodiments also may be embodied in the form of computer programcode, for example, whether stored in a storage medium, loaded intoand/or executed by a computer, or transmitted over some transmissionmedium, such as over electrical wiring or cabling, through fiber optics,or via electromagnetic radiation, such that when the computer programcode is loaded into and executed by a computer, the computer becomes anapparatus for practicing embodiments of the disclosed subject matter.When implemented on a general-purpose microprocessor, the computerprogram code segments configure the microprocessor to create specificlogic circuits.

In some configurations, a set of computer-readable instructions storedon a computer-readable storage medium may be implemented by ageneral-purpose processor, which may transform the general-purposeprocessor or a device containing the general-purpose processor into aspecial-purpose device configured to implement or carry out theinstructions. Embodiments may be implemented using hardware that mayinclude a processor, such as a general-purpose microprocessor and/or anApplication Specific Integrated Circuit (ASIC) that embodies all or partof the techniques according to embodiments of the disclosed subjectmatter in hardware and/or firmware. The processor may be coupled tomemory, such as RAM, ROM, flash memory, a hard disk or any other devicecapable of storing electronic information. The memory may storeinstructions adapted to be executed by the processor to perform thetechniques according to embodiments of the disclosed subject matter.

The foregoing description, for purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit embodiments of the disclosed subject matter to the precise formsdisclosed. Many modifications and variations are possible in view of theabove teachings. The embodiments were chosen and described in order toexplain the principles of embodiments of the disclosed subject matterand their practical applications, to thereby enable others skilled inthe art to utilize those embodiments as well as various embodiments withvarious modifications as may be suited to the particular usecontemplated.

Listing of reference labels: 1 electric motor 2 electric motor 3/3A-3Dgear actuator 4/4A/4B clutch 5 differential 6 differential lock 7 wheels8/8A/8B multi-speed gearbox 9 auxiliary device 10 device 11 device12/12A/12B shaft lock 13 server 15 database 17 remote platform 20computing device 21 bus 22 display 23 fixed storage 24 processor 25removable media 26 user input 27 memory 29 network interface 30 network100 drivetrain layout 150 drivetrain layout 200 drivetrain layout 250drivetrain layout 275 drivetrain layout 300 drivetrain layout 400drivetrain layout 500 drivetrain layout 600 drivetrain layout 700drivetrain layout 800 drivetrain layout 825 drivetrain layout 850drivetrain layout 875 drivetrain layout 900 flow 1000 flow 1300 systemconfiguration 1301 air supply 1310 hand control unit 1320 electronicbraking system control unit 1330 electronic brake modulator 1340electronic braking system one-channel module 1350 electronic brakingsystem two-channel module 1361 communication path 1362 communicationpath 1380 brake request 1400 system configuration 1410 brake booster1420 redundant foot brake module

The invention claimed is:
 1. A vehicle drivetrain for achieving abistable locking parking brake function, comprising: a multi-speedgearbox comprising: a plurality of driving stages; an actuator toactivate a first driving stage of the plurality of driving stages of themulti-speed gearbox; a first clutch to engage only the first drivingstage via the actuator; a second clutch to engage only a second drivingstage; and an elastic coupling to permit rotation of an input of themulti-speed gearbox to rotationally align the first clutch with thefirst driving stage while the second clutch is engaged with the seconddriving stage and without rotating the second driving stage, wherein theactuator can activate the first driving stage concurrently with thesecond driving stage.
 2. The vehicle drivetrain of claim 1, wherein theactuator is a first actuator and the vehicle drivetrain furthercomprises: a second actuator to activate the second driving stageconcurrently with the first driving stage activated by the firstactuator.
 3. The vehicle drivetrain of claim 2, wherein the multi-speedgearbox is a first multi-speed gearbox and the vehicle drivetrainfurther comprises: a second multi-speed gearbox comprising: a pluralityof driving stages; and a third actuator and a fourth actuator toconcurrently activate a first driving stage and a second driving stageof the plurality of driving stages of the second multi-speed gearbox. 4.The vehicle drivetrain of claim 1, wherein the multi-speed gearbox is afirst multi-speed gearbox and the vehicle drivetrain further comprises:an output shaft lock to mechanically couple an output of the firstmulti-speed gearbox with an output of a second multi-speed gearbox whilethe first driving stage and the second driving stage are concurrentlyactivated, wherein the activated second driving stage is of theplurality of driving stages of the first multi-speed gearbox or of aplurality of driving stages of the second multi-speed gearbox.
 5. Thevehicle drivetrain of claim 2, wherein the multi-speed gearbox is afirst multi-speed gearbox and the vehicle drivetrain further comprises:an input shaft lock, when activated, to mechanically couple an input ofthe first multi-speed gearbox with an input of a second multi-speedgearbox; and an output shaft lock, when activated, to mechanicallycouple an output of the first multi-speed gearbox with an output of thesecond multi-speed gearbox.
 6. The vehicle drivetrain of claim 1,wherein the first driving stage comprises a first ratio; and the seconddriving stage comprises a second ratio different from the first ratio.7. The vehicle drivetrain of claim 1, further comprising: an auxiliarydevice to manually deactivate the first driving stage or the seconddriving stage.
 8. A commercial vehicle comprising: at least one drivenaxle, at least one service brake, at least one propulsion engine, a pairof wheels, and the vehicle drivetrain of claim
 1. 9. The commercialvehicle of claim 8, further comprising: an elastic coupling, wherein asliding clutch comprises the first and second clutch, and the slidingclutch further comprises: a toothed selector ring coupled to the elasticcoupling that allows for limited rotational movement of the toothedselector ring about a sliding axis of the sliding clutch.
 10. Thecommercial vehicle of claim 8, further comprising: a sliding clutch,when actuated by the actuator, to engage the first driving stage and thesecond driving stage concurrently.
 11. The commercial vehicle of claim8, further comprising: a differential lock to mechanically link the pairof wheels.
 12. The commercial vehicle of claim 11, wherein thedifferential lock is configured to be activated to mechanically link thepair of wheels in response to, or simultaneously with, the concurrentactivation of the first and second driving stages.
 13. A vehicledrivetrain for achieving a bistable locking parking brake function,comprising: a first multi-speed gearbox comprising: a plurality ofdriving stages; and at least one actuator to activate a first drivingstage of the plurality of driving stages of the first multi-speedgearbox, wherein a first actuator of the at least one actuator canactivate the first driving stage concurrently with a second drivingstage; a first clutch of the first multi-speed gearbox to engage thefirst driving stage; a second clutch of the first multi-speed gearbox toengage the second driving stage; and an elastic coupling disposedbetween the first clutch and the second clutch, wherein the elasticcoupling permits limited relative rotation between the first clutch andthe second clutch.
 14. The commercial vehicle of claim 8, wherein thebistable locking parking brake function acts on both wheels of the pairof wheels.
 15. The commercial vehicle of claim 8, wherein the bistablelocking parking brake function permits each wheel of the pair of wheelsto rotate in opposite directions.
 16. A vehicle drivetrain for achievinga bistable locking parking brake function, comprising: a first clutch ofa multi-speed gearbox to engage a first driving stage or a seconddriving stage via a first actuator; a second clutch of the multi-speedgearbox to engage the second driving stage via a second actuator; and anelastic coupling mechanically linked to the second clutch, wherein theelastic coupling permits rotation of an input of the multi-speed gearboxto align the first clutch with the first driving stage while the secondclutch is engaged with the second driving stage.
 17. The vehicledrivetrain of claim 16, wherein the first and second actuators areconfigured to activate the first and second driving stages concurrently;and the elastic coupling permits rotation of the input of themulti-speed gearbox to align the first clutch with the first drivingstage while the second driving stage is concurrently activated andwithout rotating the second driving stage.